How to configure fail2ban with systemd journal?

For systemd systems:

You have to specify the backend in /etc/fail2ban/jail.conf to use systemd as follows:

backend = systemd

Then restart fail2ban:

systemctl restart fail2ban

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Edit:

I'm a heavy CentOS/RHEL/Fedora guy so you may have to adapt what I say a bit. As far as this answer, you may have to update the fail2ban package to a version that supports systemd as a backend or you'll have to install rsyslog and add the following to your /etc/rsyslog.conf:

authpriv.*      /var/log/auth.log

This will make sure sshd auth logs are logging to /var/log/auth.log which will be read by the default pyinotify backend in fail2ban:

You'll need fail2ban version 0.9.0 which can support systemd, while Debian Jessie has 0.8.3 in the repository.

Try downloading and installing from sources, or look for the alternative repos.

Regards.